1. Field of the Invention
In fuel injection valves, actuators are used, such as piezoelectric actuators or magnet valves. Triggering the actuators initiates a pressure relief of a control chamber, causing an injection valve to open, so that fuel can be injected into the combustion chamber of an internal combustion engine. However, magnet valves have the property of tending to bounce, and as a result the performance graph for the quantity, that is, the injection quantity, can vary so much relative to the triggering time that it is only conditionally suitable for reproduction or for compensation functions.
2. Description of the Prior Art
European Patent Disclosure EP 0 562 046 B1 discloses an actuation and valve assembly with damping for an electronically controlled injection unit. The actuation and valve assembly for a hydraulic unit has an electrically excitable electromagnet assembly with a fixed stator and a movable armature. The armature includes a first and a second surface defining a first and second hollow chamber, and the first surface of the armature is oriented toward the stator. A valve connected to the armature is capable of carrying a hydraulic actuating fluid from a sump to the injection system. A damping fluid can be collected there relative to one of the hollow chambers of the electromagnet assembly and drained away from there again. By means of a region of a valve needle protruding into a central bore, the fluidic communication of the damping fluid can be selectively opened and closed in proportion to the viscosity of this fluid.
German Patent Disclosure DE 101 23 910.6 pertains to a fuel injection system used in an internal combustion engine in which the combustion chambers are supplied with fuel via fuel injectors. The fuel injectors are acted upon in turn via a high-pressure source; moreover, the fuel injection system includes a pressure booster which has a movable pressure booster piston. This piston divides a chamber that can be connected to the high-pressure source from a high-pressure chamber that communicates with the fuel injector. The high fuel pressure in the high-pressure chamber can be varied, by filling a back chamber of a pressure boosting device or by evacuating fuel from this back chamber of the fuel booster.
In magnet valves of the prior art, the stroke length is defined by stop sleeves, to name one example. In addition, in magnet valves that have two seats, the stroke of the magnet valve can be defined by the two seats. In such magnet valves, bouncing can occur at the first, upper seat. The same is true for a valve that is open when without current and that has only one seat. If stop sleeves are received in the magnet core, they surround a closing spring that acts on the magnet armature. By means of a stop sleeve, the precise adjustment of a remanent air gap between the magnet core and the magnet armature, or its armature plate, can be accomplished. In fast opening of the magnet valve, which is desired, the armature comes to strike one face end of the stop sleeve, which is called armature bouncing. The armature bouncing on the stop sleeve has effects on the quantity performance graph, or in other words the injection quantity of fuel, relative to the triggering duration of a magnet coil of a magnet valve that actuates a fuel injector. In some applications, the effects of armature bouncing on the quantity performance graph are wanted, such as if a preinjection quantity plateau is desired for a phase of preinjection into the combustion chamber. However, in conjunction with regulating a preinjection quantity, as will be needed for fuel injection systems expected in the future, a quantity performance graph that has a preinjection quantity plateau is extremely unfavorable.